Reported "lightstep.tracer_version" is empty

Hi,

starting with v0.30.1 the library reports an empty string as the 'Client Library' version to LightStep.

https://github.com/lightstep/lightstep-tracer-java/blob/0.30.1/lightstep-tracer-jre/src/main/java/com/lightstep/tracer/jre/Version.java

Is this on purpose?